At present, a user interface board of broadband access device based on digital subscriber line (XDSL) technology can provide various access methods, for example, one or more than one of the following methods, Asymmetric Digital Subscriber Line (ADSL), Very High-Bit Rate Digital Subscriber Line (VDSL), Ethernet, Symmetric High-Bit Rate Digital Subscriber Line (G.shdsl), and etc. Meanwhile, a broadband access device may provide a plurality of user interface boards.
With development of various xDSL techniques towards wider bandwidth and higher speed, the requirements on the bandwidth and speed of xDSL lines become higher and higher. To meet such requirements, a method currently used is increasing the speed on a single pair and, meanwhile, increasing the transmission bandwidth by increasing extra high-frequency points. However, according to the transmission theory, higher frequency band means faster attenuation speed. Therefore, in the case of long distance, data transmission still depends on signals in lower frequency band. As a result, the available bandwidth of the xDSL line is decreased dramatically with the increase of the line length.
Another method for meeting such requirements is providing wider bandwidth by binding multiple lines. That is, multiple pairs of lines are provided for one user, and meanwhile, the speed of each pair of lines may be increased. In order to ensure the binding of multiple pairs of lines, however, the transmission speed of each pair of lines has to be set as the same. In actual applications of DSL techniques, however, the activated speed of each pairs of lines with equal length from the same original point to the same destination point is variant due to various factors, such as wireless wave, ambient humidity, and other factors bringing changes to line resistances and ground balance. Therefore, the activated speeds of the multiple pairs of lines from the same Central Office (CO) to the same remote user may be different. As a result, it is impossible to provide a user with a bandwidth by simply binding the multiple pairs of lines.